By using radiofrequency and terahertz spectroscopy (frequencies 1 Hz to 10¹⁴ Hz), at temperatures 0.3 K to 300 K, we have studied excitations of an ensemble of single water molecules that are caged within subnano-sized (0.5 nm) voids formed by ions of the beryl (Be₃Al₂Si₆O₁₈) crystal lattice. Measurements on dehydrated samples allow to extract absorption lines caused exclusively by water molecules, on the background of phonons resonances. In the infrared range, well-known H₂O intramolelular modes ν1 (symmetric elongation), ν2 (bending), and ν3 (asymmetric elongation) of the H₂O are observed. Spectra recorded below 1000 cm⁻¹ reveal rich set of highly anisotropic absorption bands of the low-energy response of caged H₂O molecules. Performing the DFT analysis we can assign the bands to librational and translational vibrations of separate water molecules that are weakly (van der Waals) coupled to the cages’ ldquo;walls”. At terahertz frequencies, we detect clear signs of emerging incipient ferroelectric phase within water molecules that are coupled via long-range dipole-dipole forces, with the shorter-range hydrogen bonds “switched off” due to large (4 to 9 Angstroms) intermolecular spacing. On cooling from room temperature, the static permittivity increases according to the Curie-Weiss law as a collective ferroelectric soft mode develops in the terahertz frequency range. At temperatures below 10 K, quantum fluctuations eventually suppress the ferroelectric phase transition and lead to a saturation of the soft mode parameters and of the static permittivity. We describe our results within the framework of a mean-field microscopic model that considers rotational and librational motions of interacting water molecular dipoles in a six-well potential.